Production of organic sulphur compounds



Patented Jan. 26, 1943 raonuc'nos or oacmc sorrmm comounns J Alva C.Byrns', Palos Verdes Estates, Calif., as-

shoot to Union Oil Company or California, Los Anxeles, Calif., acorporation of California No Drawing. Application February 12, 1940, i 1Serial No. 1

I 8 Claims. -(Cl. 260-609 This invention relates to a process forseparatins and recovering organic sulphur compounds from hydrocarbonfractions containing the same.

In a more specific sense the invention is concerned with'a process forselectively extracting sulphur compounds from petroleum fractions inwhich they are present and the isolation and recovery of these sulphurcompounds in usable from from the extracts.

It is well known that petroleumcrude oil distillatss contain varioustypes of organic sulphur compounds. The amounts and types of thesesulphur compounds present in any particular distillate fraction willdepend primarily on the source of the crude oil and previous treatmentsuch as distillation, cracking, contact with sulphuric acid, contactwith caustic soda solution, etc. For example, it has been shown thatfractions derived from any petroleum crude oil by distillation andboilingoveraranseof 100'F.to400' F.wil1 contain varying proportions ofmercaptans, alkyi ent invention to produce petroleum distillates ofrelatively low sulphur content. 1

I have now discovered that at ordinary atmospheric temperatures,anhydrous aluminum chloride readily forms complexes with various typesof organic sulphur compounds such as those commonly found in petroleumfractions namely,

thiophanes, allgvl sulphides, alkyl disulphides, etc.

sulphides, alkyl disulphides, thiophenes and thlophanes.

It has been recognized that sulphur compounds of acidic character, suchas the mercaptans, can 'be more or less readily removed and recoveredfrom petroleum distillates. by treatment of the latter with aqueouscaustic soda solution and subsequent acidification of the separatedaqueous phase. However, such a treatment fails to remove any of thealkyl sulphides, alkyl'disulphides, thiophaues and thiophenes which arepresent in many petroleum dis'tillates in appreciable proportions,particularly in those boiling aboveabout 200 1''. Treatment with strongsulphuric acid serves to remove sulphur compounds from petroleumdistiliates but the sulphur compoimds cannot be recovered from the acidsludse. Some attempts have been made to extract selectively the non-These complexes are-apparentlynot of definite chemical composition butmay comprise one or more molecules of aluminum chloride in combinationwith. one or more molecules of-the sulphur compounds. The complexesformed when one moi of aluminum chloride is present for each mol ofsulphur compound are fairly fluid at the usual atmospheric temperatures,are-relatively insoluble in hydrocarbons boiling below about 500 F.,particularly the lower molecular weight paramn hydrocarbons. and arereadfly decomposed by water to yield ,an aqueous phase containinghydrated aluminum chloride and an oily phase containing the sulphurcompounds- As the molal proportion of aluminum chloride to sulphurcompound isincreasedfrom 1 to 1 uptofitol oreven loto l. the solubilityof the resulting complex in petroleum hydrocarbons decreases. On theother hand as the molal proportion of aluminum chloride to sulphurcompound decreases below 1 to 1, the solb ubility of the resultingcomplex in petroleum hydrocarbons increases.

-' proportion of aluminum chloride to sulphur compound'lncreases as thetemperature is increased. However, where it is desired to avoid anyexcessive decomposition of the sulphur compounds in the complex, thelatter should not be heated to temperatures much in excess of 125' I.and deflacidic orsanic sulphur compounds present in pe-'.thesulphuroompo\mdsinusable formfromthc extracts. It is an additionalobject of the presnitely not in excess of 1 temperatures dec'omposipounds is observed and hydrosen sulphide is iib-' erated. Attemperatures much below about 30 1". 'Atmoreelevated F. the aluminumchloride-sulphur compound complexes become viscous.

The aluminum chloride-sulphur compound complexes are readilydecomposedeitherbywater orbydiluteaqueousacidsolutioni Theuse ofth'e diluteaqueous acid solutions, such as dilute bydrochloric or acetic acidsolution. for hydrolysis of the complexes to recover orsanic sulphurcompounds is preferred as hydrolysis of the aluminum chloride toaluminum oxychloride is repressed and a more rapid-separation of theoily sulphur compound phase from the aqueous phase is obtained. In thehydrolysis of the complex considerable heat is liberated and care mustbe of the sulphur com- 7 exercised that the temperature or the mixturedoes not exceed about 125 F. and definitely must not exceed 150 F.

1 In view of the aforementioned properties of aluminum chloride-organicsulphur compound complexes, I have discovered that organic sulphurcompounds can be selectively removed from petroleum fractions bytreatment of the latter with anhydrous aluminum chloride at temperaturesabove about 30' F. but not much in excess 7 of about 125 F. and below150 F. and preferably in the range of 60 to 90 F. The amount ofanhydrous aluminum chloride used toextract sulphur compounds frompetroleum fractions mayvary depending upon whether it is desired toeffect a relatively complete removal of the sulphur compounds from thepetroleum fraction or a more-efllcient utilization of the aluminumchloride. Preferably it is desired to treat petroleum fractions withabout 4.0 pounds of aluminum chloride for each 1.0 pound of'sulphurpresent in the form of organic sulphur compounds in order to obtain arelatively eflicient utilization of the aluminum chloride and at thesame time a maximum desulphurization of the petroleum fraction. Amountsof anhydrous aluminum chloride as low as about 2.0 pounds and as high asto 30 pounds per poundrof sulphur present in the form of organic sulphurcompounds can be employed where a more complete desulphurization ofthe'pa rticular petroleum fraction is desired. I

The sulphur compounds can be selectively extracted from petroleumfractions by simply adding the required amount of. aluminum chloride,intimately commingling the aluminum vchloride and petroleum fraction ata temperature below 150 F. and subsequently allowing the complex formedto collect at the bottom of they container. The treated petroleumfraction can then be decanted and the sulphur compounds recovered byhydrolysis of the extract phase in the manner previcusly describedHowever, in view of the fluid character of the aluminum chloride-organicsulphur compound complex, a more eflicient utilization of the aluminumchloride can be obtained simultaneously with a more effectivedesulphurization of the petroleum fraction by contacting the aluminumchloride with the petroleum-fraction in a counter-current manner. Thatis, aluminum chloride is introduced into the top of a treatingcolumn andis allowed 'to descend against an upwardly moving stream of thepetroleum fraction being In some a certain amount of the petroleumfraction may be mechanically occluded in the extract phase comprisingthe aluminum chloride-sulphur compound complex. This oc .cluded materialmay be eifectively removed by extraction of the with a lowboilinghydrocarbon fraction such as, pentane or butane.

Any boiling solvent remaining m -fractionandsubsequentlyjtoseparate theextract phase from fraction. said treatment being conducted at atemperature -above about 30 F. and below about 150 F. and preferably ata temperature in the range of 60 F.'to F. It is an additional object ofthe present invention to recover organic sulphur compounds in usableform from the separated aluminum chloride extract by hydrolysis ofthelatter with water or dilute aqueous acid solutions, and subsequentseparation of the oily organic sulphur compound phase from the aqueousphase, the temperature of hydrolysis being maintained below 150 F. andpreferably below about F. It is a further object to obtain fractionscomprising relatively pure sulphur compounds by fractional distillationof the recovered hydroly zate.

In the foregoing specification it was observed that aluminumchloride-organic sulphur compound complexes are somewhat soluble inhigher boiling petroleum fractions, particularly in those boiling aboveabout 500 F. but are practically insoluble in the low boilingparaflinhydrocarbons. As a result, I have found that sulphur compoundscan be effectively extracted from the higher boiling petroleum fractionsby either diluting the said fractions with one or more vol-. umes of alow boiling paraflin hydrocarbon such as, for example, propane, butane,or pentane and subsequent addition of the required amount of anhydrousaluminum chloride or treatment of the higher boiling petroleum fractionswith the desired amount of anhydrous aluminum chloride and subsequentaddition'of one or more volumes of a low boiling paraflinhydfocarbon;Obviously, the above method need not be limited to the higher boilingpetroleum fractions but can be applied if desirable to any petroleumfraction.

It is an object of the present invention to effect a more completeseparation of organic sulphur compounds from petroleum fractions,particularly those boiling above about 500 F., by dilution of the saidfractions with one or more volumes of a low boiling paraiiin hydrocarboneith'er before or after treatment of the said fractions with anhydrousaluminum chloride- Many petroleum fractions contain smal amounts ofacidic and basic compounds, such as, for example,.naphthenic acids,phenols, nitrogen bases, etc. Many of these compounds will formcomplexes with aluminum chloride and if present in the petroleumfraction will be removed into the extract along with the sulphurcompounds upontreatment with aluminum chloride; In order to conservealuminum chloride and obtain organic sulphur compounds free of suchacidic and basic materials, it is desirable to treat petroleum fractionssuccessively with dilute sulphuric acid); or v other acidic material andcaustic soda or other alkaline solution prior to treatment withanhydrousaluminum chloride in order to remove any basic and acidic materials,respectively, which may be present. On the other hand, if it is desired,the petroleum fraction may be first extracted with aluminum chloride andthe 'hydrolyzate obtained washed successively' with dilute acid andcaustic soda solution in order to remove basic and acidic compounds,respectively, extracted from the petroleum fraction by the aluminumchloride,

In the foregoing specification and in the claims, the terms "petroleumfraction and pe troleum distilla are meant to include any materialproduced from a petroleum crude oil by distillation or extraction.Furthermore, it is meant to include materials produced from petroamples:

leum crude 011 distillat'es by solvent extraction, such as, for example,a sulphur dioxide extract of kerosene or gasoline distillate. However,the terms are not meant to include materials producedby the cracking ofpetroleum fractions.

Other features, advantages and obiects of'th'e present invention willbecome apparent to those skilled in the art from the following specificex- Emmple 1 Twenty liters of a 400 F. end-point straightrun gasolinederived from Santa Maria Valley (California) crude oil by distillation,and having a gravity of 55.5 A. .P. I. at 80 1''. and a sulphur contentof 0.61% was intimately mixed at atmospheric temperature with 800 gramsof anhydrous aluminum chloride for a period of approximately two hours.i The length of the period of agitation of the aluminum chloride withany given petroleum fraction is dependent upon the efliciency of themixing and may vary from fifteen minutes to several hours depending uponthe nature of the equipment. The mixture was allowed to standv fortwelve hours in order to obtain complete separation of the extractphase. The treated gasoline was decanted from the separated extractwhich collected as a heavy tar in the bottom of the treating vessel.refined gasoline, after being washed with dilute alkali hadsubstantially the same boiling range as the untreated material andcontained only 0.072% sulphur. ,1 p

The separated. extract was washed with pentane and subsequentlyhydrolyzed with ice to obtain 323 grams of an oil having a" gravity of25.1

A. P. r. and a sulphur content r 13.7%. An ad ditional 52 grams ofsulphur compounds were obtained by extracting the aqeuous hydrolysisphase with pentane. In ali; 375 grams of extract oil were obtainedfrom'the 20 liters of gasoline treated. 1

The extract oil was dried and a 250 ml. portion was fractionated into anumber of cuts as'foi The mospheric temperature with 37.5 grams ofanhydrous aluminum chloride. on subsequent standing a small amount ofextract separated but the oil phase remained dark colored. The decanted5 oil phase was diluted with cleaners naphtha.

filtered, washed with water and the naphtha removed by distillation. Therecovered oil had a sulphur content of 3.06% indicating that only asmall proportion oi the sulphur compounds had been removed.

The above experiment was repeated under somewhat different conditions.Seven hundred and fifty milliliters of the same gas oil was diluted with500 milliliters of a hexane-heptane mixture and subsequently intimatelymixed at atmospheric temperatures with 200 grams of anhydrous aluminumchloride for onehour. An additional 250 milliliters of thehexane-heptane mixture was then added and the material allowed to standundisturbed for sixteen hours. The upper layer was then decanted,filtered. washed with water and the hexane-heptane mixture r moved bydistillation. The resultant treated oil had a sulphur content of only1.83% and a gravity of 23.8

A. P. I. The separated aluminum chloride excontent at 6.91%. IApproximately 120 grams of the recovered extract was hydrolyzed withdilute hydrochloric acid. The oil recovered from the hydrolyzate by'toppin to remove the hexane and heptane. had F.'and a sulphur a gravityof 10.8 A. P.- I. at

tract oil was fractionated under a pressure corresponding to 2 mm. ofmercury, six overhead cuts and a solid black residuebeing obtained.

. B. P.C

Cut No. at 2min. 8. Hg

Gram Pereentbgwl n0 8. 14.3 7.1 22.2 0. n1 6. 17.0 6. 14.1 NotdeterminedExample 3 One liter of an aromatic hydrocarbon fraction having a gravityof 35.8 A. P. I. at 60 1''. and a sulphur content of 0.043% and derivedfrom the so acid treatment of a sulphur dioxide extract of It will benoted that cut 1 is low in sulphur content and isprobably largely ofhydrocarbon character. Cuts 4, 5, 6, 7 and the bottoms are h her insulphur content than the crude extract. If the average molecular weightof cut 5 is assumed to be approximately .100, a reasonable assumptionconsidering the boiling range' of the material, it is readily seen thatthis fraction consists only of sulphur compounds. The

compounds in this particular fraction have been found to belargel'ythiophanes. I 1

g 7 Example 2 V i Two fifty millilitersof a heavy gas oil derivedfrom-Santa Maria Valley (California) crude oil -by'distillatiom andhaving a gravity of 18.8 A." P. I. at-BO l". and a sulphur content of3.82% was mixed at atkerosene distillate. was intimately mixed at atmospheric temperature with 15 grams of anhydrous aluminum chloride. Themixture was allowed to stand undisturbed for several hours and withwater and dilute caustic soda. The treated oil had a sulphur content oionly-0.005%. The

extract oil recovered from the hydrolysis of the extract phase had asulphur content of 2.73%.

The sulphur compounds removed from petroum distiilates iind applicationas special solvents, as odorants, and for use in chemical synthesis. Asanexample of the latter the sulphur compounds present in cut 5 ofExample 1 mentioned hereinabove have been converted into ket'ones whichexhibit excellent solvent properties and may be useful as flotationagents. The foregoing exemplary description of my invention is not to beconsidered as limiting since many variations may be made within thescope of the following claims by those skilled'in the art withoutdeparting from the spirit thereof. I-claim:

1. A method of isolating sulphur compoimds '75 from petroleum whichcomprises treating petrothe hydrocarbon phase then. decanted; washed,

leum with anhydrous aluminum choride at'a tem-' perature not lower than30 F. or in excess 01 125 F. thereby forming an aluminumchloride-sulphur compound complex, recovering said complex from saidpetroleum, hydrolyzing said complex: and separating the sulphurcompounds from the aluminum residue in the same form as said sulphurcompounds exist in the original petroleum.

2. A method of isolating sulphur compounds from petroleum whichcomprises reacting said petroleum with anhydrous aluminum chloride at atemperature of the order of 60 to 90 F. thereby forming a complexbetween the sulphur compounds contained in said oil and the aluminumchloride, separating said complex from the oil, hydrolyzing the complexwith water to liberate the sulphur. compounds and fractionating the.

sulphur compounds from the hydrolyzed mixture in the same form as saidsulphur compounds exist in the original petroleum.

proportion of one half to ten mols of aluminum 7 chloride per mol of.sulphur compound present in said oil and at a temperature between F. and125 F. thereby forming an aluminum chlo-- ride-sulphur compound complex,separating said complex from the petroleum, hydrolyzing said complex andfractlonating the organic sulphur compound from the. hydrolyzed mixturewithout any substantial change in structure of the sulphur compoundsfrom the form in which they exist in the original petroleum.

4. A process as claimed in claim 1 in which 4 a low boiling parafllnichydrocarbon is added to the petroleum to aidin the separation of thealuminum chloride-sulphur compound complex from the oil.

5. A method of isolating sulphur compounds froma hydrocarbon fractionwhich comprises contacting said hydrocarbon fraction with can'- hydrousaluminum chloride at a temperature not arating the liberated sulphurcompound from the aluminum residue. 1

6. A method of isolating sulphur compounds from a hydrocarbon fractionwhich comprises diluting said fraction with a liquid hydrocarbonfraction having a boilingpoint not substantially higher than that ofheptane, treating said diluted fraction with anhydrous aluminum chlorideat a temperature not substantialy lower than 30 F.

vor substantially higher than F. and thereby aflinic hydrocarbonfraction having a boiling point not substantially higher than that ofheptane, treating the diluted fraction with anhydrous aluminum'chlorldeat a temperature not substantially lower than 30 F. or substantiallyhigher than 125 F. and thereby forming an aluminum chloride-sulphurcompound complex, separating the complex from the hydrocarbon fraction,hydrolyzing the complex thereby liberating the sulphur compound andrecovering the liberated sulphur compound from the aluminum residue.

8. A process for the recovery-of sulphur compounds from a hydrocarbonfraction which comprises diluting said fraction with a low boilingliquid hydrocarbon selected from the group consisting of propane,butane, pentaue, hexane and heptane, contacting said diluted hydrocarbonfraction with anhydrous aluminum chloride at a temperature notsubstantially below 30 F. or substantially above 125 F. thereby formingan aluminum chloride-sulphur compound complex, separating the complexfrom the hydrocarbon fraction, hydrolyzing said complex therebyliberating the sulphur compound contained therein and recovering theliberated sulphur compound from the aluminum residue.

ALVA C. BYRN S.

